It is known that such systems, generally used for the heating of metallurgical products on the move, especially flat products, include a magnetic circuit having an air gap, a coil surrounding this magnetic circuit in the vicinity of the air gap and an electric generator supplying a current to a capacitive assembly connected to the terminals of the coil.
The temperatures employed in such electromagnetic-induction heating systems require the provision of means for protecting the coil and the neighboring structure. It is furthermore advisable to prevent any magnetic leakage flux in the region of the coil which would be liable to induce currents in the conductors of this coil, and therefore parasitic heating of these conductors. It has therefore been expedient to conceive of means enabling such parasitic heating to be limited. For example, by cooling the coil with the aid of an appropriate cooling circuit.
One of the currently known solutions therefore consists in incorporating a cooling tube in the conductor. It is this type of solution that the present invention is proposed to improve, especially so as to simplify, significantly, the production of such cooled coils while still making sure that cooling is particularly effective.
As a consequence, the present invention relates to an electromagnetic-induction heating coil, especially for the heating of metallurgical products, in which coil conductors are cooled with the aid of a tube in which a cooling fluid, in thermal contact with the conductors, circulates, characterized in that the said conductors are wound in at least one ply, as a helix around the cooling tube so that the said ply has at least one twist of one complete turn between two electrical terminals of the coil.
According to one embodiment of the present invention, the conductors are wound around the cooling tube in a plurality of plies which are crossed, superposed and wound as helices of opposite pitches.
According to another embodiment of the invention, the conductors are wound around the cooling tube in a plurality of plies which are braided over the said tube.
According to a preferred embodiment of the invention, the conductors are wound as helices around the cooling tube so as to have four turns per meter.